Many drugs and agents delivered orally suffer from poor bioavailability due to many drawbacks including poor drug absorption in the gastrointestinal tract (GI), poor stability in the GI and especially in the stomach, low solubility, etc. For all these cases there is an unmet need to overcome these drawbacks in order to improve drug bioavailability so to achieve therapeutic efficacy through effective drug delivery.
Treatment of many diseases including lethal or chronic illnesses often requires daily use of drugs or therapeutic bioactive agents, for example in the form of injection. This can result in non-compliance of the patient due to the discomfort caused by multiple administrations. In addition to being uncomfortable, injection is also expensive. Enteral delivery of such bioactive agents and drugs may provide an advantageous route for administration and may encourage patient compliance. However, oral administration of such molecules is often restricted by acid digestion of the drugs or bioactive compounds in the stomach and digestion in the small intestine. Thus, many systems focus on protecting the encapsulated molecule from degradation, and facilitating the transport of the intact molecule.
Many existing encapsulation systems for enteral delivery of drugs use biocompatible, semi-permeable polymeric capsules, enclosures or membranes, which deliver the drug to the desired release point (typically along the gastrointestinal tract) and then permit release of the drug. Other such systems use liposomes or other structures to contain the drug. Frequently, such systems provide controlled release of the drug for better therapeutic efficacy, although immediate release is also possible. The material(s) used for surrounding the drug are selected for compatibility with the active ingredient and desired release properties.
Casein, which accounts for about 80% of milk protein, is organized in micelles. Casein micelles (CM) are designed by nature to efficiently concentrate, stabilize and transport essential nutrients, mainly calcium ions and protein, for the neonate. All mammals' milk contains casein micelles. Cow's milk contains 30-35 g of protein per liter, of which about 80% is within CM.
CM are usually described as clusters of unorganized mixture of the main four caseins: αs1-casein (αs1-CN), αs2-CN, β-CN, and κ-CN (molar ratio ˜4:1:4:1 respectively (DeKruif and Holt, Advanced Dairy Chemistry-1 Proteins Part A; 3 Fox, P F; McSweeney, P. L. H., Eds.; Kluwer Academic/Plenum Publishers: New York, 2005; 233-276). The caseins are held together in the micelles by hydrophobic interactions as well as by calcium-phosphate bridges. CM form only at neutral pH and their typical sizes are in the range of 50-500 nm and their average is 150 nm.
Harnessing CM for nano-encapsulation and stabilization of hydrophobic nutraceutical substances was suggested in the prior art. Semo et al., referred to the incorporation of such CM nano-capsules in dairy products without modifying their sensory properties (Semo E. Food Hydrocolloids 2007, 21; 936-42) and further suggested their use as delivery agents of sensitive health-promoting substances using natural GRAS (generally regarded as safe) ingredients.
PCT Publication WO 2007/122613 described a system based on re-assembled casein micelles with calcium ions for the delivery of hydrophobic biologically active compounds in food and beverages. The teachings specifically relate to the incorporation of such re-assembled casein micelles into low-fat or non-fat dairy products or other food or beverage products without adversely modifying their properties. The CM are composed of sodium caseinate comprising at least the main four casein proteins and are re-assembled at neutral pH and a source of calcium ions. The reassembly of CM is enforced by flow and exposure to high pressure.
PCT Publication WO 2008/135852 described nanoparticle compositions based on a poorly aqueous soluble non-ionizable polymer, a low-solubility drug and β-casein. According to this publication, the non-ionizable polymer used in the nanoparticles, is essential for stabilizing the poorly-water soluble drug, and maintaining the drug in an amorphous form, which is needed to increase the drug poor bioavailability. In addition to being an essential component, the non-ionizable polymer constitutes ˜50% of the formulation.
U.S. Pat. No. 6,652,875 provides a formulation for the delivery of bioactive agents to biological surfaces comprising at least one isolated and purified casein protein or salt thereof in water. The disclosure relates to particular isolated and purified casein phosphoproteins in the form of casein calcium phosphate complexes intended to remain on the surface of oral cavity tissues or the gastrointestinal tract. Specific particle formation is neither taught nor suggested. Furthermore, the taught micelles comprise a casein protein selected from α-casein, β-casein, κ-casein, and mixtures thereof. This application emphasizes the need for the presence of divalent and trivalent metal ions.
U.S. Patent Application Publication No. 2002/0054914 teaches a calcium phosphate/drug core with casein micelles reconstructed as aggregates around the cores, forming micellar structures, for the delivery of pharmaceutical agents. According to that disclosure, casein molecules are arranged, presumably as micelles, around calcium phosphate particles containing the active drug, and are linked to the therapeutic agent-containing microparticles mainly by calcium phosphate and electrostatic bond interactions.
U.S. Patent Application Publication No. 2009/0029017 provides a protective system for oxidisable lipids by encapsulating them in a complex of casein and whey proteins. The emulsion is reported to stabilize the oxidisable lipid by decreasing its rate of oxidation. The emulsion is further reported to be stable upon heating which allows it to be heat treated and sterilized. However, the emulsion clearly requires a combination of both types of proteins; furthermore, the effect of low pH values and/or low temperature is not discussed. In fact, the pH is stated to be typically between 6 and 9, with the upper end of the range being even more preferred. Also the complex is stated to be formed by heating to between 70-100° C.
Casein-dextran copolymer nanoparticles encapsulating insoluble β-carotene was disclosed by Pan X. et al. (Journal of Colloid and Interface Science, 2007, 315; 456-63). The nanoparticles contained a casein and β-carotene core surrounded by a dextran shell. The particles were shown to have spherical shape with a size of about 100 nm and are stable in aqueous solution even after long term storage. The casein-dextran nanoparticles were suggested as possible delivery agents for unstable and hydrophobic nutrients and drugs. However, the teachings clearly require a casein-dextran copolymer for forming the nanoparticles.
U.S. Pat. No. 5,405,756 discloses acid soluble casein phosphopeptides prepared by enzymatic digestion of intact casein followed by step wise acidification of the digest causing precipitation of acid insoluble molecules. This procedure teaches that caseins tend to precipitate at pH values around the pI of the protein.
The use of β-casein micelles as nano-delivery vehicles for chemotherapeutic drugs was presented in the 48th Microsymposium of PMM Polymer colloids held in Prague, the Czech Republic, during July 2008, and at a scientific gathering in Hagoshrim Israel December 2008, after the priority date of the application from which the present application claims priority. There is still an unmet medical need for effective, safe and easy to manufacture delivery systems for improved bioavailability of bioactive ingredients, particularly for small organic molecules with poor solubility or poor absorption or poor stability or potential adverse effects in the GI tract.